ASHRAE-90.1-2022- - Page 104
Extracted Content
Table 6.5.7.2.2 Maximum Net Exhaust Flow Rate, cfm per Linear Foot of Hood Length
| Type of Hood | Light-Duty Equipment | Medium-Duty Equipment | Heavy-Duty Equipment | Extra-Heavy-Duty Equipment |
|---|---|---|---|---|
| Wall-mounted canopy | 140 | 210 | 280 | 385 |
| Single island | 280 | 350 | 420 | 490 |
| Double island (per side) | 175 | 210 | 280 | 385 |
| Eyebrow | 175 | 175 | NA | NA |
| Backshelf/pass-over | 210 | 210 | 280 | NA |
NA = Not allowed
c. the mechanical exhaust flow minus the available transfer air from conditioned spaces or return air ple-
nums on the same story, not in different smoke or fire compartments, and that at their closest point are within 15 ft of each other. Available transfer air is that portion of outdoor ventilation air that
-
is not required to satisfy other exhaust needs,
-
is not required to maintain pressurization of other spaces, and
-
is transferable according to applicable codes and standards and to the class of air recirculation limitations in ASHRAE Standard 62.1. Exceptions to 6.5.7.1:
-
Biosafety level 3 classified laboratories or higher.
-
Vivarium spaces .
-
Spaces that are required by applicable codes and standards to be maintained at positive pressure relative to adjacent spaces . For spaces taking this exception, any transferable air that is not directly transferred shall be made available to the associated air-handling unit and shall be used whenever economizer or other options do not save more energy .
-
Spaces where the demand for transfer air may exceed the available transfer airflow rate and where the spaces have a required negative pressure relationship. For spaces taking this exception, any transferable air that is not directly transferred shall be made available to the associated airhandling unit and shall be used whenever economizer or other options do not save more energy .
6.5.7.2 Kitchen Exhaust Systems 6.5.7.2.1 Replacement air introduced directly into the hood cavity of kitchen exhaust hoods shall not exceed 10% of the hood exhaust airflow rate.
6.5.7.2.2 If a kitchen/dining facility has a total kitchen hood exhaust airflow rate greater than 5000 cfm then each hood shall have an exhaust rate that complies with Table 6.5.7.2.2. If a single hood or hood section is installed over appliances with different duty ratings then the maximum allowable flow rate for the hood or hood section shall not exceed the Table 6.5.7.2.2 values for the highest appliance duty rating under the hood or hood section. Refer to ASHRAE Standard 154 for definitions of hood type, appliance duty, and net exhaust flow rate.
Exception to 6.5.7.2.2: At least 75% of all the replacement air is transfer air that would otherwise be
exhausted.
6.5.7.2.3 If a kitchen/dining facility has a total kitchen hood exhaust airflow rate greater than 5000 cfm then it shall have one of the following:
a. At least 50% of all replacement air is transfer air that would otherwise be exhausted. b. Demand ventilation systems on at least 75% of the exhaust air. Such systems shall be capable of and con figured to provide at least 50% reduction in exhaust and replacement air system airflow rates, including controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent, and combustion products during cooking and idle. c. Listed energy recovery devices that result in a sensible energy recovery ratio of not less than 40% on at
least 50% of the total exhaust airflow. A 40% sensible energy recovery ratio shall mean a change in the dry-bulb temperature of the outdoor air supply equal to 40% of the difference between the outdoor air and entering exhaust air dry-bulb temperatures at design conditions .
6.5.7.2.4 Performance Testing. An approved field test method shall be used to evaluate design airflow rates and demonstrate proper capture and containment performance of installed commercial kitchen
102 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)